Heat-exchanger comprising a plurality of helically wound pipe elements

ABSTRACT

In a heat-exchanger comprising a plurality of helically wound pipe elements stacked on top of each other and having their ends connected to risers all the risers are located inside the jacket of the heat-exchanger but radially outside the stack and within the same half of the circumference thereof. The design makes all the connections of the elements readily accessible and permits convenient demounting and remounting of individual elements by lateral extraction of a faulty element from the stack and reinsertion of it upon repair work. The stack is preferably composed by two or more sections any such section being provided with its own risers.

United States Patent Ostbo HEAT-EXCHANGER COMPRISING A PLURALITY OFHELICALLY WOUND PIPE ELEMENTS 5] July 17, 1973 FOREIGN PATENTS ORAPPLICATIONS 80,064 12/1955 Netherlands 165/163 487,254 10/1952 Canada"165/163 Primary Examiner-William F. ODea Assistant Examiner-William C.Anderson Attorney-Fred C. Philpitt ABSTRACT I In a heat-exchangercomprising a plurality of helically wound pipe elements stacked on topof each other and having their ends connected to risers all the risersare located inside the jacket of the heat-exchanger but radially outsidethe stack and within the same half of the circumference thereof. Thedesign makes all the connections of the elements readily accessible andpermits convenient dcmounting and remounting of individual elements bylateral extraction of a faulty element from the stack and re-insertionof it upon repair work. The stack is preferably composed by two or moresections any such section being provided with its own risers.

1 Claim, 1 Drawing Figure HEAT-EXQHANGER COMPRISING A PLURALITY FHELICALLY WOUND PIPE ELEMENTS The present invention relates to aheat-exchanger comprising a plurality of helically wound pipe elementsstacked on top of each other and having their ends connected to risersforming inlets and outlets for the one agent of the heat-exchanger, theother agent flowing in contact with the outer walls of the pipe elementswithin a space externally defined by a jacket surrounding the pipeelements.

In prior art heat-exchangers of the type above described, in which eachhelix forms a substantially circular disc and all such discs are locatedin planes perpendicular to an axis through their centres, one of therisers is at the circumference of the helix stack, whereas the otherriser extends along said axis, i.e. in the centre of the helices. Thenormal way of connecting the risers to the helices is by brazing orwelding. However, from what has just been said about the existence ofcentrally disposed risers follows that if for some reason, e.g. due tocorrosion or mechanical vibrations or following a combination of thoseor other unadvantageous operational conditions, one helical elementwould burst so that there would arise a leakage requiring replacement ofthe element, such a replacement cannot be carried out withoutsimultaneous dismounting of all other elements at either side of thedefective one. Accordingly, it will in such a situation be necessary tocup up a very considerable number of brazing or welding joints and,

upon completion of the repair work, to reconnect all of the elements byestablishing new such joints.

A further disadvantage of a heat-exchanger of the type here underdiscussion is that even if one could per se at least provisionally whilewaiting for an optimal time to carry out the repair works accept thereduction of the capacity of the apparatus caused by the disappearanceof maybe a relatively small number of elements, that expedient hasnevertheless not been available since the risers have been common to allelements.

The main object of the invention is to provide a heatexchanger in whichthe disadvantages and limitations above accounted for have beeneliminated. in accordance with the principal concept of the inventionthis has been attained by the provision of a heat-exchanger generallydesigned as above discussed but having all its risers located inside thejacket of the apparatus but radially outside the helix elements.Further, all risers extending past all helix elements are located withinthe same half of the circumference of the helices.

The most significant technical advantage resulting from such anarrangement is, that when an individual element fails, its connectionsto both risers may conveniently be cut off, since both riser tubes arereadily accessible thanks to their location outside the element stack.However, more important still is that after disconnection of the elementit can be drawn out from the stack without the need of disconnectingadjacent elements which have not failed. This does not only imply a mostimportant reduction of the repair costs proper but, above all, that thetime period necessary for carrying out such a repair work is minimizedmeaning a corresponding heavy reduction of the costs accompanying thediscontinued operation of the apparatus.

in accordance with a further significant characteristic of the inventionall the helical elements of the heatexchanger or, alternatively, allelements within a certain stack of the apparatus, are divided into twoor more sections, each such section being connected to its own pair ofrisers and all risers extending past more than one section being locatedwithin the same half of the circumference of the stack. This eliminatesthe necessity of discontinuing the operation of the complete apparatuswhen a failure does not concern all sections, it being insteadsufficient to disconnect the failing section only which is made by meansof suitable shut-off valves mounted at the related risers. There isconsequently no longer any need of a total interruption of theoperation, the only consequence of the occurrence being a reducedcapacity of the apparatus.

One embodiment of the invention will now be described in greater detail,reference being made to the accompanying drawing illustrating apart-sectional perspective view of a heat-exchanger designed inaccordance with that embodiment and having its helical elements dividedinto three sections.

The heat-exchanger illustrated in the drawing'comprises a base 1 whichover a flange connection 2 sup ports a substantially cylindrical jacket3. According to the selected embodiment the jacket is presumed toenclose one single stack of helical elements only and it is providedwith a bottom flange 4 and a top flange 5 for connection of theapparatus to a conduit traversed by the one fluid of the heat-exchanger,either the heatabsorbing or the heat-delivering agent. That agent willaccordingly flow substantially vertically through the heat-exchanger andit will during that flow contact the outer walls of the individualelements 6 of the stack. Any such element is shaped like a substantiallyflat circular disc. A plurality of such discs are mounted on top of eachother thus forming the stack. Each element is made of a pipe, usuallyconsisting of copper or steel and having each of its two ends connectedto two risers 7 and 8 by brazing, welding or in any other suitablemanner.

However, as is apparent from the drawing, only those elements locatedwithin the upper third portion of the stack are connected to risers 7and 8. The apparatus is provided with two more pairs of risers, 9, l0and 11, 12, respectively, which are located adjacent risers 7 and 8 andconnected to the elements forming the intermediate and the bottom thirdportion of the stack, respectively. Stated in other words, the stack isdivided into three sections, referenced A, B and C.

Let it now be assumed that a heat-exchanger as shown on the drawing isin operation and that one of its helical elements fails, so that aleakage resulting in unpermitted mixing of the two fluids occurs. Thenthe invention permits the following procedure.

The first step is to drain the apparatus whereupon the bolts in flangeconnection 2 are removed making it possible to lift off jacket 3. Allthe elements are now freely accessible not only to inspection of alltheir connections to the risers which connections are the most criticalpoints, especially when the apparatus is exposed to vibrations, but alsoto selective disconnection of that or those elements which have failed.The location of all risers at the circumference of the stack does notonly permit disconnection of one or more elements in a convenient way ascompared with prior art devices having centrally disposed risers butalso that, upon disconnection of one element from its risers, theelement can be horizontally displaced and taken out of the stack withoutbeing impeded by a central riser. In contrast thereto, in prior artheat-exchangers having centrally disposed risers it is, as has beenindicated above and as is directly realized, necessary to remove allelements at either side of the faulty one before the latter can bedismounted. There is, however, a second condition which must besatisfied in order to avoid additional work, namely that all risersextending along the full height of the stack are located within the samehalf of the circumference thereof. The drawing does clearly show thatthis condition is compatible with division of the stack into severalsections which in turn calls for use of a plurality of risers. It isalso obvious that a repaired or replaced element can conveniently bereconnected and that the total time necessary to carry out repair worksis considerably reduced as compared with the time consumption inconventionally designed heat-exchangers comprising helical elements.

In certain applications, such as when the heatexchanger forms part of achain of apparatus for carrying out a continuous chemical process, eventhe significantly reduced repair time realized thanks to the inventionmay involve serious disturbances. However, the invention solves thatproblem as well by division of the stack into several sections accordingto the illustrated embodiment three each such section being providedwith its own pair of risers. Those risers are then connected to tubesoutside the jacket via shut-off valves (not shown) so that theheat-exchanger can operate with one or more sections disconnected. As isdirectly understood, to be usable in that way the apparatus should whenall its sections are active be overdimensioned in relation to thenominal capacity requirement. However, calculations have clearly shownthat the higher costs for procuring such an overdimensioned apparatus ismore than outweighed by the additional safety attained, in the firstplace protection against complete interruption of the operation. Whenapplying the invention in practice, it is, alternatively, feasible todimension the heat-exchanger in the traditional way in which case thereduction in capacity occurring when a failing section has to bedisconnected is instead balanced by a reduced load up to an optimal timefor carrying out the repair works.

As appears from the above description the general inventive idea is therealization that important structural and functional advantages aregained when both ends of any individual helical elements are located atthe circumference. Since heat-exchangers of the type here at issue arenormally mounted with the longitudinal axis of the jacket disposed in avertical position terms like risers have been used here in order tosimplify the description. For the same reason the claims state that theelements are vertically stacked on top of each other. However, from whathas been said above it is clear that those terms shall not be construedin a limiting but in a descriptive sense. It has also been made clearthat the number of stacks disposed within a common jacket may be chosenarbitrarily.

I claim:

1. A heat exchanger comprising a. a plurality of separate spirally woundpipe elements positioned one above the other in a vertical array,

b. said array of spirally wound pipe elements being divided into aplurality of sections,

c. each section of spirally wound pipe elements being connected to itsown separate pair of risers,

d. each separate pair of risers comprising an inlet riser and an outletriser, and each spirally wound pipe element of the section associatedwith a given pair of risers having an inlet portion connected to theinlet riser and an outlet portion connected to the outlet riser,

e. all risers being located closely adjacent to the periphery of saidvertical array of spirally wound pipe elements,

f. all pairs of risers that extend past more than one section ofspirally wound pipe elements being located within the same half of thecircumference of said vertical array, and

g. a jacket surrounding both the aforesaid vertical array of spirallywound pipe elements and all pairs of risers, said jacket consisting ofupper and lower end wall portions and an annular side wall portioninterconnecting said two end wall portions, the annular side wallportion of said jacket completely surrounding both said array ofspirally wound pipe elements and all'pairs of risers, one end wallportion containing an inlet means for heat exchange fluid and the otherend wall portion containing an outlet means for the same heat exchangefluid, said inlet means and said outlet means being in opencommunication with both the exterior of the entire outlet means.

1. A heat exchanger comprising a. a plurality of separate spirally woundpipe elements positioned one above the other in a vertical array, b.said array of spirally wound pipe elements being divided into aplurality of sections, c. each section of spirally wound pipe elementsbeing connected to its own separate pair of risers, d. each separatepair of risers comprising an inlet riser and an outlet riser, and eachspirally wound pipe element of the section associated with a given pairof risers having an inlet portion connected to the inlet riser and anoutlet portion connected to the outlet riser, e. all risers beinglocated closely adjacent to the periphery of said vertical array ofspirally wound pipe elements, f. all pairs of risers that extend pastmore than one section of spirally wound pipe elements being locatedwithin the same half of the circumference of said vertical array, and g.a jacket surrounding both the aforesaid vertical array of spirally woundpipe elements and all pairs of risers, said jacket consisting of upperand lower end wall portions and an annular side wall portioninterconnecting said two end wall portions, the annular side wallportion of said jacket completely surrounding both said array ofspirally wound pipe elements and all pairs of risers, one end wallportion containing an inlet means for heat exchange fluid and the otherend wall portion containing an outlet means for the same heat exchangefluid, said inlet means and said outlet means being in opencommunication with both the exterior of the entire array of spirallywound pipe elements and the exterior of all pairs of risers, said pairsof risers communicating with the space exterior to said jacket by meansof passageways that extend through one of said end wall portions of saidjacket that is detachable from said annular side wall portion of saidjacket, whereby heat exchange fluid can flow into said jacket throughsaid inlet means, around both said array of spirally wound pipe elementsand all pairs of risers, and out of said jacket through said outletmeans.